The present invention relates generally to electrochromic mirror assemblies, and more particularly to a sealed electrochromic rear view mirror assembly that is especially resistant to seal ruptures caused by dendritic formation at the electrode film/adhesive layer interface.
Electrochromics is generally defined as the science of reversibly darkening materials by application of electricity. In recent years, electrochromic mirror assemblies have found increasing use in automotive applications, for example, for use in conjunction with rear view mirror assemblies. These electrochromic mirrors can offer properties such as automatic dimming (e.g., by mounting forward- and rearward-facing light/glare sensors on the mirror bracket) or dimming on demand by the press of a button (e.g., on a control console located in the passenger cabin). In operation, electrochromic mirror assemblies permit the reduction in the level of glare on the rear view mirror that is typically caused by the headlights of other automobiles approaching from the rear. However, while conventional electrochromic mirrors are in great demand, the failure rate is relatively high, resulting in costly recalls and assembly replacements, as well as consumer dissatisfaction.
A more complete discussion of electrochromic mirror assemblies, including their function, construction, and operation, can be found in U.S. Pat. Nos. 5,151,824; 5,446,576; 5,659,423; 5,808,778; 5,278,693; 4,917,477; 5,751,467; 5,128,299; 5,148,014; 5,668,663; 5,801,873; 4,465,339; and 5,808,778, the specifications of all of which are specifically incorporated herein by reference thereto.
For illustrative and comparative purposes, a typical construction of a conventional electrochromic mirror assembly 10 is shown generally in FIGS. 1-4, with particular reference to FIG. 3. As shown in FIGS. 1-4, the assembly is a laminate structure which typically includes a first glass panel 12, a second glass panel 14, and an electrochromic material 16 disposed or trapped therebetween. Electrochromic material 16 is trapped between the glass panels 12 and 14 by way of spacers 18 and 20. The mirror includes at least one reflective element 22 adjacent to one of the glass panels. Additionally, the construction requires conductive electrode films 24 and 26, which can be selectively energized to activate the electrochromic material 16 (e.g., in relatively high glare conditions) or deactivate it into its rest state (e.g., in relatively low glare conditions). Typically, the respective spacers 18 and 20 are sealed between glass panels 12 and 14 (more specifically, electrode films 24 and 26) by means of some type of adhesive material, shown in FIG. 3 as layers 28 and 30. Terminal strips 32 and 34 permit a current or potential to be imparted to electrochromic material 16 via conductive films 24 and 26.
It has been discovered by the present inventors that the failures in the prior art have been due to breaches in the seal between glass panels 12 and 14/electrode films 24 and 26 and adhesive layers 28 and 30. It has been discovered that dendrite formations, shown illustratively as 31 in FIG. 3, tend to migrate along the interface between electrode films 24 and 26 and adhesive layers 28 and 30 until the seal is eventually ruptured. Thereafter, air, water or other contaminants can migrate inside the laminate structure and discolor the mirror or oxidize the reflective surface 22.
It has also been discovered by the present inventors that these dendrites are probably formed due to ionic migration of silver or other materials from the reflective film 22 (which is typically comprised of silver palladium) or other conducting surfaces into the dendrite formation 31, especially through clip 34 and a suitable conductor such as water 35, as shown in FIG. 1.
Therefore, there exists a need for preventing or inhibiting dendrite formation in electrochromic mirror assemblies, especially at the interface between the adhesive layer and the electrode film layer.
It is accordingly an object of the present invention to prevent or inhibit dendritic growth in electrochromic mirror assemblies.
It is another object of the present invention to prevent or inhibit dendritic growth at the electrode film and adhesive layer interface of electrochromic mirror assemblies.
It is another object of the present invention to prevent or inhibit breaches in the seals of electrochromic mirror assemblies.
It is another object of the present invention to prevent or inhibit breaches in the seals of electrochromic mirror assemblies which can expose the electrochromic material and the interior of the mirror to outside contaminants.
In accordance with one embodiment of the present invention, an electrochromic mirror assembly comprised of a laminate structure is provided, wherein the laminate structure is substantially resistant to dendritic formation between adjacent layers of the laminate structure.
In accordance with another embodiment of the present invention, an electrochromic mirror assembly comprised of a sealed laminate structure is provided, wherein the sealed laminate structure is substantially resistant to breaches in the seals between adjacent layers of the laminate structure.
In accordance with another embodiment of the present invention, a process for manufacturing an electrochromic mirror assembly is provided, wherein the electrochromic mirror assembly comprises a sealed laminate structure, wherein the sealed laminate structure is substantially resistant to the formation of dendrites between adjacent layers of the sealed laminate structure, comprising:
selecting starting materials which are substantially free of water;
optionally, selecting starting materials which do not promote dendritic formation; and
in a substantially water free environment, assembling the starting materials so as to form the sealed laminate structure.
Additional objects, advantages and features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings.